Apparatus for treating drilling mud



June 5, 1956 R. w. ERwlN APPARATUSv FOR TREATING DRILLING MUD 2 Sheets-Sheet 1 Filed June 30, 1952 INVENTOR d few/N ATTORNEY June 5, 1956 R. w. ERwlN APPARATUS FOR TREATING DRILLING MUD 2 Sheets-Sheet 2 Filed Junel 50, 1952 INVENTOR United Sie@ Patent 2,74s,ss4

`APPARATUS non TREATING narrativo MUD Rans'omeV W. Erwin, FortWorth, Tex., assignor toSalt 4Water Control, Inc., Fort Worth, Tex., a corporation v'of Texas Application June 30, 1952, Serial No. 296,396

7 Claims. (Cl. 18S-2.5)

.'The inventionv relates to apparatus for treating'drilling mud.

.iIn drilling ,oil wells4 it .is now standard practice to use a circulating liquid commonly called drilling mudV for Athe purpose of cooling and lubricating the vdrill bit, removing cuttings from the hole, lubricating the drill pipe, providing cakey or seal lining foran exposedv formation hole,and as a controllable hydraulic head vor load for preventionV of premature flowing of the well. It is-'with this latter function that this inventionis chieti-y concerned. The, mud is usually made heavier by-y addition ofpulverized-.harites or barium sulfates. As the-drilled hole .goes deeper greater earth rock pressures are encountered :and thus greater oil or gas pressuresfif the driller is fortunate enough to ind them. It is standard practiceto= carry surplus weight in the drilling -mu'das' a safety factor in anticipation of abnormal gas pressures. `As the hole deepens 'the specic gravity ofthe mud is progressively increased to provide this vsafety factor. ,An ideal system would be one where the -mud is .just heavy enough to suppress'uid flows from'forma- 'tion-being drilled, with only enough additional weight to offset the lightening effect of gases released from'the drilled up formation in the well bore itself. `If the mud is much heavier than the formation pressures encountered then in many rotten or very porous' formations -the serious hazard of lost circulation or mud losstothe formation arises. Thus, the driller cannot just add a large surplus of weighting materials to his mud in order to -besurev to prevent formation flows while drilling. He must operate between two serious limitations. .If his mud is too light, hydrocarbons or salt watermay flow from the formation and blow the` mud column from .the hole'. Iff'the mud is too heavy it may break down a forma- 4tion and ow into it instead of circulating back' to the surface. If this happens with the mud being lost faster thanitf'can be replaced, then the mud column in Vthe well `will be shortened, and possibly sealed olf zones at a higher" level may break through and start flowing. '.Either of ythese two conditions may cause blowouts due to inability to control the llow, resulting in Vlossv of well, equipment, lives and even whole oil reservoirs.

But even when operating between the above limits the .process may get out of hand if, for instance, a .thick gas distillate bearing zone is being penetrated. Asathe zoneis. drilled, all .the hydrocarbons .contained .in the .drilled upzportion. are picked up by the circulatingfmud. These. may be quite condensed as liquidstunder .thepresysuresat the .drill bit, but as the mud rises totheftop of .the well-with -steadily diminishing pressure .on it, these liquefied gases turn into gases", expandand lightenthe mud .by lgasif-ying'or gas cutting it. lf this gas/is'not removed :and the mud recirculated it picks upstill more fgas, making'the mud even lighter, necessitating addition .of weightingmaterialsrif .the wellfhas not -already/ started v.iowingidueto loss of weight-controlion it. Thus,the

thorough removal of entrained gases -andllighter :liquid 2,748,884 -Patented .lune 5, 1956 ICC- hydrocarbons from the drilling mud is quite importantin drilling oil or, gas wells.

Most prior drilling rigs attempt removal of lighter com* ponents -by flowing the mud through long 4troughs or ditches and byv agitation of the mud with jet nozzle guns in mud tanks. Such prior processes have succeeded in removing only a portion of the gas, and rely oncarrying extra weight in the mud to offset gas that cannot be removed. There have been several rnud degassing devices built and used,but m'ost have been 'discarded for one reason or another. .Today the large majority of drilling rigs rely solelyonditches and mud gun jet nozzles in pits, which are farshort of whatziswanted ln the average mud system it costs about $3000.00 in labor and weighting materials to .addone `pound per gallon of weight to they mud when itsnde'nsity .is over ten or twelvepoun'ds to the/gallon. Many rigs .carry at leastvtwo` pounds per gallon extra weighton the mud purely for a margin of safety against possiblewgas cutting. Obviously, a reliable and operable mud 7degasser that would remove all gases and lighter hydrocarbon liquids from all the mud as it comes from .the well, thus breaking the accumulating cycle, would lessen' the'need. for this live or six thousand dollarswo'rt-h of extra weighting material. Also, carrying two pounds per gallon less weight would greatly lessen the likelihood of.v formation break 'down withresultant mud losses.

Thus,l the principal object of thisl invention is to'continuously and conveniently remove all or nearly all-'entrained or dissolved gases and light liquid 'hydrocarbons fromall the drilling'mud in van oil or gas -well'dr'illing operation as it comes from the well and prior to its circulation' back into the well.

'Another object is to provide an eicient apparatusfor removing this gas with complete wash flushing out facilities to obviate formation of hard mud cake and sediment in said apparatus.

Another object is to provide a mud degasser with no valves or moving parts inthe ow path of the mud. This isvimportant because of the abrasive nature of the mud and its tendency to coat up and clog up all'parts it contacts.

Another object is to provide an unrestricted owpath through the degasser with no small ports or openings that could beplugged by coarse material in the mud.

Another object of this 'invention is to provide a small compact -apparatus that'is designed to provide the same surfacearea 'exposure that only a much larger vessel or container would oifer in other degasser designs; one that ts easily astride any mud trough on a drilling` rig .without additional iloor space.

Another object is, by use of high vacuum'and great area exposureof mud, to removegases without the violent agitation .or centrifuging kcharacteristic of certain other mud degassers. It has been found that while centrifugal whirling of the mud separates gas from it, such action Ialso throws out suspended weighting material, which tends todefeat its purpose.

:It has been observedthat aeration of Vgas cut mud in some cases facilitates removal of the gas. The present invention provides 'for'admixture and agitation of mud with air justas the mud enters the vacuumed degasser, if 'conditions warrant it. However, it should be V'noted that a great excess vof air should be added toavoid chances of making an explosive mixture of air and gases.

Another object is to provide vacuumed cascading of vthe mud without gas and mud interference or countergas withdrawal vacuum. pump.

Another object is to provide a mud degasser so arranged that in case of its shutdown for any reason, accidental or otherwise, the circulating mud will automatically bypass the degasser and assume the path it would have followed if no mud degasser were provided.

Another object is to provide a qualitative gas detector that will record and notify the driller when hydrocarbon gas is being removed from mud. By recording this on a chart with a clocking arrangement synchronized with a drilling depth log chart, it is possible to determine approximately the depth of the bit when the gas is produced.

Another object is to meter the removed gases giving important meaning to such data since in this process all of the mud is being completely and continuously degassed. This step too, can be synchronized and correlated with a well depth log which is a conventional apparatus now in use on many drilling rigs.

Gas detectors and alarms are now available and in use on mud streams in some drilling rigs, but unless substantially all the gas is removed from the mud prior to its circulation back into the well a qualitative gas indication would have little or no meaning. However, if all gas is removed in the muds cycle, then the gas detector provided on this mud degrasser or in the mud stream ahead of it would hold much meaning and logging information. My object is to provide substantially gas-free mud reentering the drilling well to give meaning to gas detecting efforts.

Where it is convenient to use electric power to drive the motor on the gas evacuating pump it is an object of this invention to provide still another gas indicating and metering device. I have found that when no gases are being produced with the mud, the vacuum pump does little work, thus using a minimum of electric power in the motor. However, as soon as any gas is produced the pump starts doing work, immediately putting a proportionate power demand on the motor. Thus, a power meter on the circuit of the motor, both visible and recording, would provide another gas logging method. This log would indicate all gases being handled, both air and hydrocarbons. If produced water vapour should confuse this power measurement logging method then it may be removed by placing a dessicant dryer in the suction line to the vacuum pump. In many cases this would be constant and its removal unnecessary.

Another object of the invention is to so locate the mud degasser that, if desired, mud containing all the bit cuttings will pass through the degasser before undue exposure to atmosphere. The novel design of the mud degasser so exposes the oil and gas formation cuttings to an intense vacuum that many of the hydrocarbons inherent in their pore spaces will be evacuated by the vacuum pump. With the use of an instrument now on the market, it is possible to qualitatively record and indicate whether the hydrocarbons are light like methane, or are heavier gasoline vapours. If they prove to be gasoline vapours then this fact would indicate oil or gas distillate formation cuttings, as contrasted to dry gas.

I believe that I am the first to provide a practicable method for insuring thorough and complete exposure of all the well cuttings to a vacuum for removing hydrocarbon. This is accomplished by extensive surface exposures and cascading of all the mud. This novel design also makes ample provision against undue dropping out of sediments and cuttings by avoiding large volume settling spaces, due to its compact and constant travel design. It provides maximum surface exposure with minimum volume space. If some of the cuttings do settle out they may be completely ushed out periodically by a novel washing arrangement. Water, which is often added as liquid make up to the system, may be used for ushing out these cuttings, or pressured degassed mud from a conditioner pump may be used when no water is needed in the mud system.

The invention will be more readily understood by reference to the accompanying drawings and to the following detailed description in which the invention is illustratively embodied.

In the drawings:

Fig. l is a perspective view somewhat diagrammatic in character of my combined mud degasser and hydrocarbon logging device;

Fig. 2 is a diagrammatic view showing the mud degasser and hydrocarbon logging device with connections to a well undergoing a rotary drilling operation, some of the details of the degasser and hydrocarbon logging device which are shown in Fig. l being omitted for simplicity and to more clearly illustrate the system as a whole; and

Fig. 3 is a vertical section through the degasser taken substantially on line 3-3 of Fig. 1.

Referring first more particularly to Figs. l and 3, gas cut mud from source 1 enters a mud trough 2 through outlet 3 prior to entry into a mud degasser tank 62. The source is usually the shale shaker or discharge from a choke manifold, or it may be the drilling well head itself, ahead of the shale shaker. The mud degasser tank 62 may be a welded pressure vessel approximately three feet in diameter and about ten feet long. It is mounted horizontally astride the ruud trough 2, somewhere between the mud line choke manifold from the drilling well and the usual mud conditioning pits, one of which is shown at 69 in Fig. 2. The gas cut mud is picked up by vacnum from the sand trap or sump 4 through suction pipe inlet 5. This pipe is usually a light gauge 8" diameter conduit that may be adjusted for suction depth by means of dresser union 7. The gas cut mud is pulled into the top portion of the degasser at 8 through a cut-a-way overow pipe 9 open at the top, the end of which is capped at 10. Periodically the pipe 9 should be thoroughly ushed out by high pressure wash water from perforated wash pipe 42 within the pipe 9.

The gas cut mud overlows from the open topped pipe 9, radially, then passes down over a pair of downwardly and outwardly inclined cascade plates 11. These plates spread the mud out into a thin sheet of considerable area, thus, subjecting the mud to eight or ten inches of vacuum by means of which the entrained and dissolved gases are removed. Also, any highly volatile liquid hydrocarbons such as distillates will be vaporizcd and flashed. The mud is further exposed by passing from plates 11 to a pair of downwardly and inwardly inclined cascade plates l2 (Fig. 3) back towards the center of the degasser vessel. Then the mud falls onto a pair of inclined roof top cascade plates 13 to split into two streams, going to the lower part of the degasser shell.

At this point all or most of the gas should be now removed from the mud. The degassed mud now enters a U-type liquid seal discharge 15 at outlet 14. This device also comprises a light gauge 8" diameter conduit pipe whose suction inlet is in the head of the vessel as near the bottom of the shell as is possible to construct. The degassed mud passes through the discharge pipe 15 and into a reducing jet housing 17 at the point 16. The jet housing 17 may be removed for cleaning or inspection by screwing it out of the coupling 39. The degassed mud is pulled from the vacuumed degassing vessel 62 by means of a jet nozzle 38. This is usually a 3/4" orifice mud conditioning gun nozzle which may be reached for cleaning or changing by unscrewing pipe 17 from the coupling 39. The source of jet power for this nozzle is preferably pressured mud from the conditioner circulating pump. The pressured mud preferably comes from a pump 70 (Fig. 2) to enter the jet system at 39 through valve 37. The mud is expanded through jet nozzle 38, pulling out degassed mud and re-entering the mud trough at 18. From here the degassed mud passes, conventionally, to a cuttings removing shale shaker 67 (Fig. 2) and then to one or more mud tanks or pits 69 to be picked up by one or more mud pumps 70 for return to the drilling well. i

avang'ssa A's the gases"(airand hydrocarbons) are `removed from the large exposed mud surfaces, .it is vitaliyimportant to remove them with a minimum of countercurrent contact with a curtain of .cascading mud. This is e'iciently accomplished by special pairs of vent pipes 65. Only one pair is shown, but the degasser preferably has several pairs of these vent pipes, which also act as tie ymembers between the cascade plates. These vent pipes receive lgas through openings 19, 2i) and 21 (Fig. 3). Opening 19 at the top takes gas removed from vthe first pair of cascade plates 11. Opening receives gas removed from the roof top cascade plates 13. Opening 21 receives gas removed from mud as it flows from the bottom of shell 62 to outlet 14. Gas removed from the second pair of 'cascadeplates 12 goes directly rto a main gas outlet or pick up pipe 23. All other gas picked up through aforedescribed vent pipes 65 goes out opening 22 to main outlet pipe 23.

All the .removed gases pass through main y pickup pipe 23 .and through a .float actuated valve 24 having. a float 59. The float-5.9 will rise with the mud level in `the Idegasser in case of .flooding and shut off valve 24 before mud reaches the gas discharge pipe 23, thus precludingthe possibility of pulling mud .into the gas discharge outlet. The removed .gas passes up discharge riser 25` through pipe union S8. This pipe union 58 permits facile re- ...moval of gas pickup pipe 23 and valve 24 `for cleaning, repair or inspection. The gas goes'up through ani-nver-ted U-riser kloop 26, and then passes down into a conventional float actuated liquid -trap 28 (oat not shown) at point 27. .Riser .loop 26 is high enough to make the lifting .of heavy mud to its peak impossible, should the .float valve .24 fail. This `is another safety precaution to avoid pulling mud into 4the vacuum pump 32. yShould any foam or .-liquidcondensates form or carry over with the gasses,

it will be :caught in trap 28. The .internal 'construction vof the trap is not shown, as it is a well known and widely .used appliance. When the liquid .builds up in the trap, -a yoat closes the outlet,A thus preventing pulling liquids into vacuum pump 32. Gases pass .from float ltrap 28 'through outlet 29, then through lpressure reducing regu- 'lator 30 to vacuum pump 32 atentrance 31. This conventional `vacuum pump 32, which may be driven by any vpower desired or convenient, discharges the gases at 33 to pass through gas detector 34. The gas ldetector is kanother Widely used `instrument that indicates the .slightest trace of yhydrocarbon gases. A direct readingmeter 61 may be placed where the driller can see it -by connect- .ing wires 60. Also, a recording chart (not shown) may be incorporated in this setup. The gas passes on .from gas detector 34 through a conventional gas meter 63 to atmosphereat 35, Gas 'meter 63 can be a recording type, thereby facilitating -the use of this `Setup .for gas logging and correlation.

Another feature of the invention is the controlled aeration of the mud, if needed. Many muds give up )their hydrocarbon gases more readilywhen air is mixed with them, and they are 'then subjectedto vacuum for removal of air and hydrocarbons. This may be .readily accomplished Vin this system by means of the wash .pipe 42 in Aoverflow pipe 9. Instead of using water in wash pipe 42, as would normally be the case, air inlet ivalve 64 maybe yopened. (with water valve 41 closed) kthus thoroughly laerating and agitating mud lin pipe -9 just prior to its over- 'iiow into the degasser.

lThe importance of beingable to thoroughly and easily Ywash `every part .of Vthe degasseris very great. The .tendencyof mud Ato-coatand `cake upon the surfaces lis lwell known and has always been a serious problem in mud handling equipment. lf allowed to go too long, some of it sets and becomes almost as hard as portland cement. It, therefore, is highly important that this cake accumulation, as well as sand and cuttings sediments, be periodically ushed out of mud handling devices. It is for this '6 reason that so much attention' is given washingV jetsand Wash pipes in this vmud degasser design.

Wash Water from a pump (not shown) providing both great volume and pressure, cornes to a wash pipe manifold at 40 (Fig. l). If there is a water source of `ample volume and pressure, all Wash valves 49, 41, 43, 45 and 47 may be opened at once to wash down and flush out the degasser when it is notin operation. If there is a limited volume in the water supply, then each wash pipe valve should be operated singly. Valve 41 controls the supply of wash water to perforated wash pipe 42 within the open topped inlet pipe 9, which Washes out inlet pipe 9. Valve 43 controls wash water to a pair of perforated wash pipes 44, which wash down the rst pair of cascade plates 1`1. Valve 45 controls wash water to perforated wash pipes 46, which wash down the second or lower pair of cascade plates i2. Valve 47 controls wash water to a'double row perforated wash pipe 48, which washes down each side of roof top cascade plates 13. Valve 49 controls wash water to Wash pipe 50, which contains jet .nozzles 51 `for 'flushing sediment from the bottom of degasser shell to outiet 14. Discharge pipe 15 contains a drain valve 5319 be opened when the .degasser 62 is being washed down.

For inspection and Vmanual cleaning, if needed, man- Way 57 at the front end of shell 62 isprovided to .permit access to all cascade baffles. The manway also ypermits access Vto the iioat 59 and valve 24 on the gas discharge pipe assembly.

Vacuum gauges 54, 55 and 56 providea picture o'f functions in the system. if the tank tends to flood .and valve 24 closes, then vacuum gauge 54 will read less than gauge 55. If regulator 30 fails to function, .then gauges 55 and 56 will probably read the same, whereas normally regulator 30 will provide less vacuum on gauge 55 'than yon gauge-56. If the float valve is closedjin the `drip pot 28 the vacuum in Vgauges 54 and S5 will both go to zero, while 56 will shown an abnormally high vacuum. v

Reference will now ybe made more particularly .to Fig. 2 of the `drawings which diagrammatically V'illustrates .the mud cycle and gas handling only .but does ynot attempt to show baffling or washing feature details of the 'degasser itself, these having been already described in connection with Figs. l and 3.

Gas free high pressure mud from pump 70 is forced through pipe 71 to drill pipe 73 at drill pipe entrance 72. The mud goes down inside the drill .pipe and comes out vthrough the drill bit 74. The .drill bit .is assumed to be operating in a .freshly drilled, exposed gas formation 75. kThis mud flows out of the bit, lubricating and coo'ling it, picks up drilled formation `cuttings and passes out through an annular space between the hole 75' or casing liner 76 and drill pipe 73. Since it is .in a gas zone, the mud picks up entrained gases from cuttings and gas that may escape .before the porous wall yis plastered with the mud. The .mud with the entrainedgases rises up .through annular space to well head `77 .and Vpasses out through the discharge pipe at 1. The mud enters the sand trap or lreception well 4 and yis sucked into mud degasser 62 by .pipe 8.

In the degasser 62, by cascading the mud through a vacuum, most or all of the gaseous hydrocarbons are removed and Withdrawn by vacuum pump 32 through outlet pipe 23. The gas passes successively through float `actuated valve 24, outlet pipe .25, inverted U-riser 42,6, automatic .shut-oif liquid trap 28, vacuumfreducing liegulator 3i), vacuum pump .32, qualitative electronic gas detector 34, volume gas meter 63 and thence toatmosphere at 35. Recording and visible power meter on vacuum pump 32 measures electric gpower consumed by the pump motor, giving a direct indication of the work performed by vacuum pump. Recording and visible electronic hydrocarbon meter 61 on gas detector 34 gives a qualitative record of the hydrocarbon gases exhausted from the mud degasser.

The degassed mud is rapidly passed on out of the degasser 62 with subjection to no dead spaces or volume retention that would permit settling of cuttings or weighting materials. The degassed mud then goes through outlet 14 to liquid seal legs 15, through reduced jet housing pipe 17 and back into mnd trough 2 at 18. The mud is pulled from the degasser by the jetting action of high pressure degassed mud. The high pressure mud comes from high pressure line 71 at 36, through valve 37 and out through jet nozzle 38. It rejoins the low pressure degassed mud, which passes on to the cuttings removing shale shaker 67. The mud leaves the shale shaker, goes down mud ditch 2 to discharge 68 where it dumps into mud pit or tank 69. From here the mud is picked up by pump 70 for recycling back into the drilling well.

Should the degasser 62 fail to pick up all the mud entering sand trap 4, this mud would rise up and ow over the darn 100 which, as shown, is higher than the intake 5 of pipe 8, and thence on down mud trough 2 directly to shale shaker 67, and on to the mud tank 69. This automatically acts to avoid interruption of the mud cycle, which is of vital importance in the drilling operations.

Manhole 57 at the end of tank 62 is provided to give complete inspection and cleaning access to cascade baiiies and oat actuated gas outlet valve 24.

If, for any reason, accidental or otherwise, the suction iiow through the degasser should be stopped, the sand trap 4 would ll with mud which would well up and travel down the mud trough 2 to shale shaker 67 and on to outlet 68 and thence to mud pits 69. Thus, the mud degasser would automatically be by-passed, avoiding any confusion or loss of mud. This novel suction and discharge arrangement makes this possible.

The invention has been described in detail for the purpose of illustration, but it will be obvious that numerous modifications and variations may be resorted to without departing from the spirit of the invention.

I claim:

l. An apparatus for continuously degassing mud, comprising a closed mud degassing vacuum tank having an inlet conduit for gas-laden mud, an outlet conduit for degasilied mud leading from the tank, and means for causing the tiow of mud into, through and out of said mud degassing tank, said means comprising a jet nozzle for discharging mud into the outlet conduit beyond the degassing tank, and means for supplying degassed mud under pressure to said jet nozzle.

2. In a drilling mud degassing system, a closed mud degassing vacuum tank having an inlet pipe for gas laden mud, means, including a receptacle, for receiving degassed mud from the degassing tank, means, including an outlet pipe from the degassing tank, for discharging degassed mud from the degassing tank into the receptacle, a mud return pipe leading from the receptacle to the degassing tank outlet pipe having a jet nozzle for discharging mud into said outlet pipe beyond the degassing tank, and pump means in said return pipe between said receptacle and said jet nozzle for applying pressure to the returned mud, said jet nozzle serving to draw mud into, through and out of said degassing tank.

3. In a mud degassing system, a mud degassing vacuum tank having an inlet for gas-laden mud and an outlet for degassed mud, a passageway for degassed mud leading from the degasser, liquid seal means interposed between the passageway and the mud degasser outlet, a mud re-circulating means comprising a pipe connected at one end to the passageway and communicating at its other end with a jet at the exit from the liquid seal means at a point beyond the mud degasser outlet, and a circulating pump in said return pipe, whereby returned mud e 8 serves to draw mud to be treated into, through and out of the degasser vacuum tank.

4. In a drilling mud degassing system, a mud degassing vacuum tank having an inlet pipe for gas-laden mud, a receptacle for degassed mud from the degassing tank, liquid seal means interposed between the degassing tank and the receptacle, a mud return pipe leading from the receptacle to the liquid seal, a jet nozzle in said return pipe at the exit from said seal means and beyond the degassing tank, and a pump in said return pipe for supplying pressure to the circulating mud, said jet serving to draw mud into, through and out of said degassing tank.

5. In a drilling mud degassing system, a receptacle for gas-laden mud from the drilling well, a mud degassing vacuum tank having an inlet pipe communicating with said receptacle, a second receptacle for degassed mud from the degassing tank, a liquid seal interposed between the degassing tank and the second receptacle, a mud return pipe leading from the second receptacle to the liquid seal, a jet nozzle in said pipe at the exit from said seal and beyond the degassing tank, and a pump in said return pipe for supplying pressure to the circulating mud, said jet serving to draw mud into, through and out of said vacuum tank.

6. In a mud degassing system, a horizontally extending mud conduit, having a receptacle at each end, a closed vacuum mud degasser tank extending above the mud conduit and receptacles, said degasser tank having an inlet pipe for mud to be degassed extending into the first receptacle and an outlet conduit for discharging degassed mud leading into the second receptacle, the first receptacle having overow means leading to said conduit at a level above the degasser inlet, whereby untreated mud would rise in the first receptacle and overflow through the conduit in case of stoppage through the degasser.

7. In a system of handling drilling mud including a drilling well having a mud inlet leading thereto and an outlet therefrom for gas-laden drilling mud, a receptacle for receiving gas-laden mud from said well outlet, a second mud receptacle spaced down stream from the first receptacle, a closed mud degasser vacuum tank above the receptacles having an inlet pipe extending into the first receptacle and an outlet conduit for degassed mud leading to the second receptacle, means for returning mud under pressure from the second receptacle to the drilling well, and an overflow mud conduit means above the entrance to the inlet pipe and leading from the iirst mud receptacle to the second for bypassing drilling mud directly to the second receptacle without passing through the degasser, in case of stoppage of said mud degasser.

References Cited in the tile of this patent UNITED STATES PATENTS 1,401,101 Ehrhart Dec. 20, 1921 1,433,966 Mills Oct. 31, 1922 1,452,253 Nevitt Apr. 17, 1923 1,667,139 Borden Apr. 24, 1928 1,863,111 Greve June 14, 1932 1,940,007 Moore Dec. 19, 1933 2,082,329 Foran et al June l, 1937 2,142,270 Vander Henst Jan. 3, 1939 2,195,898 Newton Apr. 2, 1940 2,241,273 Robinson et al May 6, 1941 2,243,176 Vander Henst May 27, 1941 2,289,687 Stuart July 14, 1942 2,555,314 Buckley et al June 5, 1951 2,622,694 Pryor Dec. 23, 1952 2,663,379 Doan Dec. 22, 1953 

1. AN APPARATUS FOR CONTINUOUSLY DEGASSING MUD, COMPRISING A CLOSED MUD DEGASSING VACUUM TANK HAVING AN INLET CONDUIT FOR GAS-LADEN MUD, AN OUTLET CONDUIT FOR DEGASIFIED MUD LEADING FROM THE TANK, AND MEANS FOR CAUSING THE FLOW OF MUD INTO, THROUGH AND OUT OF SAID MUD DEGASSING TANK, SAID MEANS COMPRISING A JET NOZZLE FOR DISCHARGING MUD INTO THE OUTLET CONDUIT BEYOND THE DE- 